<?php
class Student{
    private $surname;
    private $first_name;
    private $emails;
    private $grades;

function __construct($surname, $first_name)
{
$this->surname = $surname;
$this->first_name = $first_name;
$this->emails = array();
$this->grades = array();
}
function add_email($which, $address)
{
$this->emails[$which] = $address;
}
function add_grade($grade)
{
$this->grades[] = $grade;
}
function average()
{
$total = 0;
foreach ($this->grades as $value)
$total += $value;
return $total / count($this->grades);
}
function toString()
{
$result = $this->first_name . ' ' . $this->surname;
$result .= ' (' . $this->average() . ")\n";
foreach ($this->emails as $which => $what)
$result .= $which . ': ' . $what . "\n";
$result .= "\n";
return '<pre>' . $result . '</pre>';
}

}